Since the ban on international trade of ivory in 1989, the ivory black market has been on the rise, and a National Geographic investigation found that demand for religious art pieces carved out of the precious material has played a considerable role.

“No matter where I find ivory, religion is close at hand,” said investigative reporter Bryan Christy, whose article, “Ivory Worship,” is included in the new edition of National Geographic magazine, released Friday (Sept. 14).